Keyer control circuit for electronic musical instruments

ABSTRACT

In an electronic musical instrument including playing keys and respectively associated tone keyers, each tone keyer is keyed by a control signal producing circuitry. The control signal producing circuitry comprises a coil inducing an electromotive force responsive to the depressing speed of the associated key having a magnet, a capacitor charged with the induced electromotive force through a first diode, a discharging circuit consisting of a second diode and a resistor, the second diode being connected in the forward direction for a discharging current of the capacitor, and a normally open switch associated with the key and connected between the juncture of the second diode and the resistor and a voltage source for reversely biasing the second diode, wherein the control signal for the tone keyer is derived from the capacitor. This construction prevents the instrument from producing cipher which would otherwise occur due to the failure of closure of the switch which is associated with the key.

0 United States Patent 1151 3,657,463 Hiyama [451 Apr. 18, 1972 54]KEYER CONTROL CIRCUIT FOR 3,544,695 12/1970 Dijksterhuis ..s4/1.13ELECTRONIC MUSICAL 3,553,337 1/1971 Dijksterhuis ..84/l.13 INSTRUMENTSPrimary Examiner-Laramie E. Askm Inventor! 'Y Hamamatsu- P AssistantExaminer-Stanley J. Witkowski [73] Assignee: Nippon Gakki Suzo KabushikiKaisha, Anomeycushman Darby Cushman Hamamatsu-shi, Japan [57] ABSTRACT[22] Filed: Nov. 17, 1970 In an electromc mus1cal instrument includingplaying keys and PP No.1 90,294 respectively associated tone keyers,each tone keyer is keyed by a control signal producing circuitry. Thecontrol signal [30] Foreign Application Priority Data producingcircuitry comprises a coil inducing an electrometlve force responsive tothe depressing speed of the associated Nov. 18, 1969 Japan ..44/92253key having a magnet, a capacitor charged with the induced 1969 Japan 3 3--44/92254 electromotive force through a first diode, a dischargingcircuit Nov. 18, 1969 Japan ..44/109351 consisting ofa second diode anda resistor, h second diode 1 being connected in the forward directionfor a discharging [5%] [1.8.5] ..84/1-26, 84/l.l3 currem of thecapacitor and a normally open Switch 2 gi 1/072 sociated with the keyand connected between the juncture of 1 0 care the second diode and theresistor and a voltage source for reversely biasing the second diode,wherein the control signal [56] References Cited for the tone keyer isderived from the capacitor. This construction prevents the instrumentfrom producing cipher UNITED STATES PATENTS which would otherwise occurdue to the failure of closure of the sw1tch which 1s associated with thekey. Re.27.0l5 12/1970 Di ksterhuis et a1 ..84/1.15 3,567,839 3/1971Dijksterhuis ..84/l.26 7 Claims, 13 Drawing Figures 8A K TONE ,1, L o. Q'O rm XI. KEYER Patented April 18, 1972 3 Sheets-Sheet 1 FIG,

TONE KEYER FIG. 2

SAI

TONE KEYER 7 IN NTOR.

flTTo/a A1575 Patent ed April 18, 1972 3,657,463

3 Sheets-Sheet 2 T|ME-- FIG. 6 FIG. 40 0 FIG. 4b

OUTPUT SIGNAL LEVEL HTTDRIUEY Patented April 18, 1972 3,657,463 5Sheets-Sheet :3

FIG. 7 J'ILT; A

TONE +Vcc "H to J I 5L; 2 g5 2 INVE TOR.

MM) AMYYW HTfORII EYS BACKGROUND OF THE INVENTION 1. Field of theInvention The present invention relates to a keyer control circuit forelectronic musical instruments, and more particularly, to an improvedkeyer control circuit in a keying system for the instrument of the typedescribed and capable of producing the so-called touch-responsive toneenvelope effect such that a keyed tone signal has an amplitude or toneenvelope in accordance with the intensity of depression of an associatedkey, i.e., the depressing speed of the key.

2. Description of the prior art Recently, there has been proposed anarrangement of a touch-responsive tone envelope control circuit for anelectronic musical instrument having a keyer tone control circuittherein, which comprises a coil directly grounded at one end thereof andadapted to vary the interlinking magnetic fluxes in association with thedepression of a playing key arranged on a keyboard of the instrument,e.g., the key carrying a magnet thereunder, the other end of said coilbeing grounded through a series circuit of a rectifying element such asa diode and a capacitor for storing an electromotive force induced inthe coil responsive to the key depressing, and a key-operated normallyclosed switch having a movable contact connected between the capacitorand the diode and a stationary contact grounded through a resistor andcapable of being actuated in association with the operation of theassociated key, the movable contact being also connected to a controlterminal of a keyer circuit for receiving a control signal from thearrangement and thereby triggering the keyer. In such an arrangement,however, a fear for the occurrence of cipher has been unavoidable due tothe failure of a perfect closure of the contact of the above-mentionednormally closed switch. even when the switch is not actuated by theassociated key, resulting in an extremely bad effect of the music beingplayed.

SUMMARY OF THE INVENTION It, therefore, is the principal object of thepresent invention to provide an improper keyer control circuit for usein a keying system of an electronic musical instrument, which is capableof completely preventing occurrence of cipher due to trouble of theswitch contact.

Another object of the present invention is to provide an improved keyercontrol circuit capable of securely and reliably controlling a keyer inassociation with depressing of a corresponding key.

A further object of the present invention is to provide an improvedkeyer triggering circuit which makes it possible to provide a so-calledtouch-responsive tone envelope effect of an improved respondence of thetone intensity to the key depressing speed.

A still further object of the present invention is to provide a keyertriggering circuit capable of operating in close response to even theslowest speed of the key depression.

Other objects, features and advantages of the present invention willbecome apparent from the following detailed description taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic circuit diagramillustrating an embodiment of the present invention.

FIG. 2 is a schematic circuit diagram illustrating another embodiment ofthe present invention.

FIGS. 3a to 30 and FIGS. 4a to 4c are graphs for explaining thefunctions of the circuits shown in FIGS. 1 and 2, respectively.

FIGS. 5 and 7 are schematic wiring diagrams illustrating otherembodiments of the present invention.

FIGS. 6 and 8a and 8b also are illustrations for explaining thefunctions of the circuits shown in FIGS. 5 and 7, respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereunder, like symbols andreferences indicate like parts in the drawing.

Referring to FIGS. 1 and 3, a tone keyer control circuit according to anembodiment of the present invention will be described, in which Ldesignates a coil grounded at one end thereof and arranged to vary theinterlinking magnetic fluxes in association with depression of anplaying key K arranged on a keyboard of an'electronic musicalinstrument, which key carries a magnet thereunder, and the other end ofsaid coil is grounded through a rectifying element D and a capacitor Cboth being connected in series to each other. The juncture d between theelement D and the capacitor C is grounded through a series circuitconsisting of a unidirectional element Do and a resistor R theconnection point r between which is connected via a make switch S, Le, aswitch having a normally open contact associated with the key K andoperative responsive to the key depression to a DC power source +Vcc.The juncture dis also connected to a control terminal of a known tonekeyer circuit SA which may be constituted by gating elements such asdiodes and FETs (field effect transistors) and of which the detail willbe omitted here. The tone keyer circuit SA is provided with its inputterminal tl adapted to receive tone signal and its output terminal toadapted to derive that tone signal as its output signal in associationwith the depression of the key.

Thus, the number of the tone keyer control circuits and the keyercircuits SA which are installed in the console of the instrumentcorresponds in number to tone generators (not shown) or the playingkeys, for example, sixty-one.

In operation, when any one key K provided in the instrument isdepressed, amagnetic member-which may be either magnetized or notmagnetized and which may be attached to the key-moves toward or awayfrom the fixed coil L, thereby resulting in a damped pulse voltagewhichis approximately proportional to the intensity or the speed ofdepression of the playing key-due to variations in interlinking fluxesestablished around the coil, as shown by a waveform in FIG. 3a. Theinduced voltage would theoretically be a DC pulse, but as a matter offact the voltage presents an alternating shape due to bound of the key,a stray capacity of the coil, etc. The induced alternative voltage isrectified through the diode D and as a result, positive DC componentsdeveloped at the diode D are stored in the capacitor C, as shown bycurves in FIG. 3b. At the same time, the make switch S is closed inresponse to the key depression to reversely bias the unidirectionalelement Do at positive voltage of the power source +Vcc, which isrendered to be non-conducting, and as a result, the voltage stored onthe capacitor C is kept at the control terminal of the tone keyer SA, sothat a tone signal applied to the input terminal t1 may be successivelyderived at the output terminal to at a level corresponding to thedepressing speed of the key as shown by curves in FIG. 3c until releaseof the key.

Then, upon release of the key being depressed, the key is made restoredby its self-retum action and simultaneously, the switch S is opened, sothat no reverse bias voltage is applied across the unidirectionallyconducting element D0, which element is rendered in its conducting stateand therefore, the charge stored on the capacitor C at a voltage inducedin response to the depressing speed of the key discharges in a shortperiod of time through the element D0 and the resistor R having arelatively low resistance. As a result, the gating element in the keyercircuit SA is reverse biased into its non-conducting state, and hence,no tone signal is developed at the output terminal to.

In the operation of the depressing key, an oscillative voltage inducedin the coil L is responsive to the intensity of depression of the key Kor the depressing speed of the key in magnitude. Accordingly, a quick orstrong key depression makes the storage voltage of the capacitor Chigher to render the tone output level at the keyer greater, while aslow or weak key depression brings a small tone output level. Thus, thepresent arrangement makes it possible to achieve a keyer control withso-called touch-responsive tone envelope effects in the electronicmusical instrument. For example, this arrangement permits to provide apiano play effect.

Referring to FIG. 2, there is shown another embodiment of the presentinvention, in which the circuit connection is somewhat different fromthat of FIG. 1. That is, one end of a coil L1 is connected to the powersource +Vcc and the other is grounded through a rectifying element D1and the capacitor C1 all connected in series. The connection point d1between the element D1 and the capacitor C1 is connected via a seriescircuit of the unidirectionally conducting element D and the resistor R1to the power source +Vcc. At the point r1 between the element D10 andthe resistor R1 is connected the key actuated normally open change-overswitch S1 whose opposite end is grounded. The connection point d1 isalso connected to the control terminal of the gating element in saidkeyer circuit SAl. In this case, the gating element is of the type inwhich it makes a non-conducting state when its control electrode beingabove a predetermined positive potential.

The operation of the arrangement will be described similarly to thepreceding embodiment.

Initially, in the inoperative condition of the normally open switch S1,the capacitor C1 is supplied with a positive voltage via the resistor R1and the unidirectional conducting element D10 from the power source +Vccand charged at that voltage. At that time, the gating element of thekeyer circuit SA! is in its non-conducting state, and accordingly, nooutput signal is developed at the output terminal r10 of the keyer SAl.

When the key K is depressed a damped pulse voltage-is produced acrossthe coil L as shown by a waveform in FIG. 4a, as similarly as describedabove. During the negative half wave duration of the produced voltage,the positive voltage stored on the capacitor C1 is discharged via therectifying element D1, thus dropping the voltage across the capacitorC1. At that time, the switch S1 is also actuated to close its contactwith the point r1 being rendered at the ground potential, so that thediode D10 is rendered in its non-conducting state to shut the powersource off from the capacitor C1. Accordingly, the voltage across thecapacitor C1 takes waveforms as shown in FIG. 4b having a drop portionlower than the initially charged voltage, whereby the conduction of thegating element of the keyer SA] is controlled. Thus, it will be seenthat the tone input signal applied to the keyer SAl can be derived atthe output terminal r10 in response to the key depression, as shown bywaveforms in FIG. 4c.

Upon release of the key being depressed, the switch S1 is made open toforward bias the diode D10 into its conducting state. Then, thecapacitor C1 can be charged from the power source +Vcc and accordingly,the voltage across the capacitor C1 is increased above the predeterminedvoltage at which the gating element of the keyer SA] is rendered in itsnon-conducting state. Thus, the keyer is shut off by release of thedepressed key.

FIG. 5 shows a modification of the preceding embodiments which comprisesa transistor Q as a class amplifier to amplify a voltage induced acrossthe coil L in response to the depressing speed of the key. The base ofthe transistor Q is grounded through the coil L, the emitter is groundedthrough a resistor R and the collector is connected through a loadresistor R3 to a relatively high direct current voltage source +Vcc andthrough a series circuit of a diode D2 and a resistor R2 to a relativelylow DC voltage source +Ve, e.g., half of +Vcc whereby the keyer SA canbe controlled to provide the tone volume responsive to the keydepressing speed in two rates depending on the ranges of the depressingspeed of the key. The collector is also connected through a diode D inthe forward direction for a negative going pulse to a grounded capacitorC. The juncture point a is connected to a gate control terminal of thekeyer SA. The gate control portion of the keyer circuit SA is normallyheld at a relatively high voltage by the capacitor C being fullycharged, at which the gating element is rendered in its non-conductingstate. The capacitor C is charged through a diode D1 and a resistor R1by the DC power source +Vcc upon opening of the key-actuated normallyopen switch S, i.e., a make switch. The circuit operation of thisarrangement can be said to be effected as shown in FIGS. 3a, 4b and 4c.When the key K is depressed a damped pulse voltage is produced acrossthe coil L as shown by a waveform in FIG. 3a. The positive cycles of thevoltage are amplified by the transistor 0 into negative going cycles atthe collector. These negative going voltages discharge through the diodeD the capacitor C which has been normally charged up to +Vcc through theresistor R1 and the diode D1. Accordingly, the voltage at the point dgoes down as shown in FIG. 4b, which in turn gates the tone signal asshown in FIG. 40. Within a certain range of the depressing speed of thekey, i.e., where the negative peak of the collector voltage does not gobelow +Ve, the diode D2 never conducts and accordingly the volume iscontrolled by the depressing speed at a higher rate. But over thatrange, i.e., where the negative peak of the collector voltage go below+Ve, the diode D conducts and accordingly the volume is controlled bythe depressing speed at a lower rate.

In FIG. 6, the relation between the key depression speed and the outputvolume is shown, in which a chain line is desirable and a solid line isundesirable to provide effects playing piano. This is due to theselection of the values of the elements and the potential of the DCsource +Ve.

Referring to FIG. 7, there is shown a further modification of FIG. 5,which is characterized by a circuit used in common to all keyer controlassemblies, as shown by a block E for improving the linearity of theoutput of each transistor and automatically effecting thermalcompensation for the transistor, in place of having the series circuitof the resistor R2 and the diode D2 connected to the DC source +Ve asshown in FIG. 5. That is, the coil L is grounded through a parallelcircuit composed of a diode D2 and a capacitor C2 at its one endopposite to that connected to the base of the transistor Q. Said one endof the coil L is connected through a resistor R4 to the DC voltagesource +Vcc. The line 1 is kept at a certain small voltage due to theforward voltage drop of the diode D2.

Thus, a predetermined voltage is applied to the base of the transistor,and the characteristics of its base-emitter voltage VBE vs. its basecurrent 15 which would otherwise be of a solid line in FIG. 8a iscompensated to be as a chain line in FIG. 8a, and as a result thecharacteristics of the output signal level vs. the depressing speed ofthe key which would otherwise be of a solid line in FIG. 8b iscompensated to be as a chain line in FIG. 8b, thereby eliminating anon-sensitive region of the key depression. The diode D2 acts as athermal compensation for the transistor 0 as well known in the art. Theelements having the same references as FIG. 5 are of the same functions.

I claim:

1. A tone keyer control circuit for use in an electronic musicalinstrument having at least a manually depressable single playing keyhaving a magnet mounted thereon and at least a single tone keyercomprising:

a coil for mounting adjacent said key so that depression of said keyinduces a voltage signal in said coil having an amplitude which varieswith the speed with which said key is depressed,

a first diode connected to said coil for receiving and rectifying saidinduced voltage,

a capacitor connected to said first diode so as to change its voltagefrom an initial voltage in response to the rectified signal,

an initial voltage return circuit connected to said capacitor comprisinga serially connected resistor and second diode connected so that currentnormally flows through said capacitor via said second diode and registerwhen said capacitor voltage is changed to return said capacitor voltageto its initial voltage,

a first terminal adapted for receiving a direct current voltage,

plurality of transistors, each transistor having a base cona normallyopen switch mounted so at to close by the depression of said key andconnecting the junction between said second diode and said resistor tosaid first terminal,

means for providing a voltage at said first terminal so that 5 saidsecond diode is reverse biased to prevent flow of current through saidsecond diode, which would cause the voltage of said capacitor to returnto its initial voltage, so long as said switch remains closed, and

means for connecting said capacitor to said tone keyer.

2. A circuit as in claim 1 further comprising an amplifier locatedbetween said coil and said first diode for amplifying the inducedsignal, and a series circuit comprised of a third diode and a secondresistor and connected between the output side of the amplifier and acommon DC voltage source providing a relatively low voltage than that ofthe preceding DC source, to thereby provide a variety of control modesin accordance with the depressing speed of the key.

3. A circuit as in claim 2 wherein said amplifiers include a nected tothe coil, an emitter grounded through a resistor and a collectorconnected to a DC source through a load and said first diode.

4. A circuit as in claim 3 wherein at least one common diode is providedto connect with each base of each of said transistors for maintainingthe base voltage at a predetermined value, thereby providing thelinearity of the each induced output signal responsive to the depressingspeed of the respective key and temperature compensation.

5. A circuit as in claim 1 wherein each said capacitor is normallyenergized by said DC voltage source at a predetermined voltage to rendera gating element of the keyer to be cutoff, while the voltage at thecapacitor is reduced upon depression of the associated key to rendersaid gating element to be conducting.

6. A circuit as in claim 1 wherein said direct current voltage receivedat said first terminal is ground.

7. A circuit as in claim 1 wherein said direct current voltage receivedat said first terminal is a positive voltage.

1. A tone keyer control circuit for use in an electronic musicalinstrument having at least a manually depressable single playing keyhaving a magnet mounted thereon and at least a single tone keyercomprising: a coil for mounting adjacent said key so that depression ofsaid key induces a voltage signal in said coil having an amplitude whichvaries with the speed with which said key is depressed, a first diodeconnected to said coil for receiving and rectifying said inducedvoltage, a capacitor connected to said first diode so as to change itsvoltage from an initial voltage in response to the rectified signal, aninitial voltage return circuit connected to said capacitor comprising aserially connected resistor and second diode connected so that currentnormally flows through said capacitor via said second diode and registerwhen said capacitor voltage is changed to return said capacitor voltageto its initial voltage, a first terminal adapted for receiving a directcurrent voltage, a normally open switch mounted so at to close by thedepression of said key and connecting the junction between said seconddiode and said resistor to said first terminal, means for providing avoltage at said first terminal so that said second diode is reversebiased to prevent flow of current through said second diode, which wouldcause the voltage of said capacitor to return to its initial voltage, solong as said switch remains closed, and means for connecting saidcapacitor to said tone keyer.
 2. A circuit as in claim 1 furthercomprising an amplifier located between said coil and said first diodefor amplifying the induced signal, and a series circuit comprised of athird diode and a second resistor and connected between the output sideof the amplifier and a common DC voltage source providing a relativelylow voltage than that of the preceding DC source, to thereby provide avariety of control modes in accordance with the depressing speed of thekey.
 3. A circuit as in claim 2 wherein said amplifiers include aplurality of transistors, each transistor having a base connected to thecoil, an emitter grounded through a resistor and a collector connectedto a DC source through a load and said first diode.
 4. A circuit as inclaim 3 wherein at least one common diode is provided to connect witheach base of each of said transistors for maintaining the base voltageat a predetermiNed value, thereby providing the linearity of the eachinduced output signal responsive to the depressing speed of therespective key and temperature compensation.
 5. A circuit as in claim 1wherein each said capacitor is normally energized by said DC voltagesource at a predetermined voltage to render a gating element of thekeyer to be cutoff, while the voltage at the capacitor is reduced upondepression of the associated key to render said gating element to beconducting.
 6. A circuit as in claim 1 wherein said direct currentvoltage received at said first terminal is ground.
 7. A circuit as inclaim 1 wherein said direct current voltage received at said firstterminal is a positive voltage.